
Entanglement quantification in split spin-squeezed states.— As a second application, we quantify bipartite entanglement between two systems, \(A\)  and \(B\) . An entanglement criterion suitable to this scenario is the one derived by Giovannetti et al. in Ref. [1]}, stating that all separable states of two collective spins satisfy
\(\mathcal {G}^2:= \dfrac{\Delta ^2( g_z J_z^A + J_z^B) \Delta ^2( g_y J_y^A + J_y^B) }{\left(|g_zg_y| \left|\left\langle J_x^A \right\rangle \right| + \left|\left\langle J_x^B \right\rangle \right| \right)^2 /4} \ge 1 \) 
